SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c5fbfeb6735bc39e2cbedfbf795aecf493128d8be0d91c2240f82d2ef5c8535' 
  AND token = 'BksSBTb7jRLCHZUXjrWn8aBRLEllYZml1qVOCnXvJwQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}